usb: gadget: uvc: track frames in format entries

Just like the header is tracking the formats in a linked list, in this
patch we track the frames in a linked list of the formats. It
simplifies the parsing of the configfs structure.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>

Link: https://lore.kernel.org/r/20220421211427.3400834-6-m.grzeschik@pengutronix.de


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>